/*
 * 
 * JSMin.java 2006-02-13
 * 
 * Updated 2007-08-20 with updates from jsmin.c (2007-05-22)
 * 
 * Copyright (c) 2006 John Reilly (www.inconspicuous.org)
 * 
 * This work is a translation from C to Java of jsmin.c published by
 * Douglas Crockford.  Permission is hereby granted to use the Java 
 * version under the same conditions as the jsmin.c on which it is
 * based.  
 * 
 * 
 * 
 * 
 * jsmin.c 2003-04-21
 * 
 * Copyright (c) 2002 Douglas Crockford (www.crockford.com)
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * The Software shall be used for Good, not Evil.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package org.jsvm.util.javascript;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PushbackInputStream;

public class JSMin {
    private static final int EOF = -1;

    private PushbackInputStream in;
    private OutputStream out;

    private int theA;
    private int theB;

    public JSMin(InputStream in, OutputStream out) {
        this.in = new PushbackInputStream(in);
        this.out = out;
    }

    /**
     * isAlphanum -- return true if the character is a letter, digit,
     * underscore, dollar sign, or non-ASCII character.
     */
    static boolean isAlphanum(int c) {
        return ((c >= 'a' && c <= 'z') || (c >= '0' && c <= '9')
                || (c >= 'A' && c <= 'Z') || c == '_' || c == '$' || c == '\\' || c > 126);
    }

    /**
     * get -- return the next character from stdin. Watch out for lookahead. If
     * the character is a control character, translate it to a space or
     * linefeed.
     */
    int get() throws IOException {
        int c = in.read();

        if (c >= ' ' || c == '\n' || c == EOF) {
            return c;
        }

        if (c == '\r') {
            return '\n';
        }

        return ' ';
    }

    /**
     * Get the next character without getting it.
     */
    int peek() throws IOException {
        int lookaheadChar = in.read();
        in.unread(lookaheadChar);
        return lookaheadChar;
    }

    /**
     * next -- get the next character, excluding comments. peek() is used to see
     * if a '/' is followed by a '/' or '*'.
     */
    int next() throws IOException, UnterminatedCommentException {
        int c = get();
        if (c == '/') {
            switch (peek()) {
            case '/':
                for (;;) {
                    c = get();
                    if (c <= '\n') {
                        return c;
                    }
                }

            case '*':
                get();
                for (;;) {
                    switch (get()) {
                    case '*':
                        if (peek() == '/') {
                            get();
                            return ' ';
                        }
                        break;
                    case EOF:
                        throw new UnterminatedCommentException();
                    }
                }

            default:
                return c;
            }

        }
        return c;
    }

    /**
     * action -- do something! What you do is determined by the argument: 1
     * Output A. Copy B to A. Get the next B. 2 Copy B to A. Get the next B.
     * (Delete A). 3 Get the next B. (Delete B). action treats a string as a
     * single character. Wow! action recognizes a regular expression if it is
     * preceded by ( or , or =.
     */

    void action(int d) throws IOException, UnterminatedRegExpLiteralException,
            UnterminatedCommentException, UnterminatedStringLiteralException {
        switch (d) {
        case 1:
            out.write(theA);
        case 2:
            theA = theB;

            if (theA == '\'' || theA == '"') {
                for (;;) {
                    out.write(theA);
                    theA = get();
                    if (theA == theB) {
                        break;
                    }
                    if (theA <= '\n') {
                        throw new UnterminatedStringLiteralException();
                    }
                    if (theA == '\\') {
                        out.write(theA);
                        theA = get();
                    }
                }
            }

        case 3:
            theB = next();
            if (theB == '/'
                    && (theA == '(' || theA == ',' || theA == '='
                            || theA == ':' || theA == '[' || theA == '!'
                            || theA == '&' || theA == '|' || theA == '?'
                            || theA == '{' || theA == '}' || theA == ';' || theA == '\n')) {
                out.write(theA);
                out.write(theB);
                for (;;) {
                    theA = get();
                    if (theA == '/') {
                        break;
                    } else if (theA == '\\') {
                        out.write(theA);
                        theA = get();
                    } else if (theA <= '\n') {
                        throw new UnterminatedRegExpLiteralException();
                    }
                    out.write(theA);
                }
                theB = next();
            }
        }
    }

    /**
     * jsmin -- Copy the input to the output, deleting the characters which are
     * insignificant to JavaScript. Comments will be removed. Tabs will be
     * replaced with spaces. Carriage returns will be replaced with linefeeds.
     * Most spaces and linefeeds will be removed.
     */
    public void jsmin() throws IOException, UnterminatedRegExpLiteralException,
            UnterminatedCommentException, UnterminatedStringLiteralException {
        theA = '\n';
        action(3);
        while (theA != EOF) {
            switch (theA) {
            case ' ':
                if (isAlphanum(theB)) {
                    action(1);
                } else {
                    action(2);
                }
                break;
            case '\n':
                switch (theB) {
                case '{':
                case '[':
                case '(':
                case '+':
                case '-':
                    action(1);
                    break;
                case ' ':
                    action(3);
                    break;
                default:
                    if (isAlphanum(theB)) {
                        action(1);
                    } else {
                        action(2);
                    }
                }
                break;
            default:
                switch (theB) {
                case ' ':
                    if (isAlphanum(theA)) {
                        action(1);
                        break;
                    }
                    action(3);
                    break;
                case '\n':
                    switch (theA) {
                    case '}':
                    case ']':
                    case ')':
                    case '+':
                    case '-':
                    case '"':
                    case '\'':
                        action(1);
                        break;
                    default:
                        if (isAlphanum(theA)) {
                            action(1);
                        } else {
                            action(3);
                        }
                    }
                    break;
                default:
                    action(1);
                    break;
                }
            }
        }
        out.flush();
    }

    class UnterminatedCommentException extends Exception {
    }

    class UnterminatedStringLiteralException extends Exception {
    }

    class UnterminatedRegExpLiteralException extends Exception {
    }
}
